ESTIMATION OF ACOUSTIC AGGLOMERATION OF AEROSOLS PROCESS FOR SOURCE - - PowerPoint PPT Presentation

ESTIMATION OF ACOUSTIC AGGLOMERATION OF AEROSOLS PROCESS FOR SOURCE TERM MITIGATION IN NUCLEAR ACCIDENTS

Manuel Aleixandre1, Enrique Riera1, Rosario Delgado-Tardaguila2, Luís E. Herranz2 and Juan A. Gallego-Juárez1

1Department of Sensors and Ultrasonic Systems, ITEFI, CSIC (Madrid, Spain)

Unit of Nuclear Safety Research, CIEMAT (Madrid, Spain)

UIA46 Symposium, 24-26 April 2017, Dresden, Germany

Outline

• Motivations
• Objectives
• Experimental Program and Results
• Development of Numerical Model
• Comparison of Experimental and Numerical Results
• Scaling up – Simulations Results
• Synthesis

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MOTIVATIONS (1)

• After the TEPCO Fukushima accident of March 2011 one of the main concerns of nuclear industry has

been the search for improved atmospheric source term mitigation

• Several countries in Europe and China had already implemented Filtered Containment Venting

Systems (FCVS) before and after the Fukushima accident Filtered Containment Venting Systems (FCVS)

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MOTIVATIONS (2)

• New national R&D programmes and new coordinated international activities on Filtered

Containment Venting Systems (FCVS) were promoted

• Call for offers launched by European Commission in 2012
• PASSAM: “Passive and Active Systems on Severe Accident source term Mitigation”

PASSAM OBJECTIVES

The PASSAM project is of R&D experimental nature mainly on FCVS, aiming at:

• Exploring potential enhancement of existing source term mitigation devices, and
• Demonstrating the ability of innovative systems to achieve larger source term attenuation

such as Acoustic Agglomeration of Aerosols (AAA)

• To produce simple models and/or correlations based on the understanding of the physical

phenomena involved

• To generate a valuable database which may be strategic for helping the utilities and

regulators in assessing the performance of the existing source term mitigation systems

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AAA OBJECTIVES

Specific Objectives:

• To develop an Mitigative System Acoustic Agglomerator (MSAA) and

integrate it in the PECA facility

• To measure and characterize the aerosol growth inside the MSAA
• To find out the best operational conditions of the MSAA to work with

the aerosols to be generated during the experiments.

• To measure aerosol lifetime with and without fostering acoustic

agglomeration

• To estimate the practical requirements of a MSAA system in a real

scenario Facilities:

• PECA (Platform for Experimental Characterization of Aerosols)

Investigate the performance of an acoustic agglomerator system at lab-scale under anticipated conditions

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EXPERIMENTAL PROGRAM

EXPERIMENTAL SET-UP Platform for experimental Characterization of Aerosols (PECA) Gas supply system; Aerosol generator; Injection line; PECA vessel; Exhaust line Instrumentation and sampling Instrumentation and control of the thermal-hydraulic variables Real time devices (APS, ELPI) Gravitational devices (mass cascade impactors and membrane filters) Sampling Mitigation System by Acoustic Agglomeration (MSAA) A parallepipedic chamber; 2 Power ultrasonic transducers (21kHz, 155dB, 300W/unit) MEASUREMENTS During the experiments the effect in the aerosol concentration and its distribution was characterized by several magnitudes: Reduction of the aerosol mass concentration Reduction of the aerosol number concentration Increase of aerosol particle size

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EXPERIMENTAL PROGRAM

Selected Boundary Conditions for the Aerosol Particles

• 1. Reproduction as close as possible of the real conditions of the aerosols
• a. Particle size between 0.3 μm and 2.5 μm
• b. SiO2 and TiO2 aerosols
• c. Concentrations on the range of 25-200 mg/m3
• d. Ambient conditions (temperature, humidity...)
• 2. Reproducible and known conditions of aerosol that facilitate future modeling
• a. High monodisperse and well characterized particles
• b. Mixture of monodisperse well characterized particles
• c. Controlled and characterized input mass concentrations
• d. Controlled and characterized treatment time in the ultrasound field

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EXPERIMENTAL PROGRAM

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EXPERIMENTAL MATRIX

Total number of tests 20

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EXPERIMENTAL MATRIX

Each test consisted of two phases and were conducted 2 times Flush sub-phase: aerosol generator OFF, ultrasound OFF, gas flow =200 kg/h

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EXPERIMENTAL RESULTS

Ultrasound Effects: Particle Number Concentration

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EXPERIMENTAL RESULTS

Ultrasound Effects: Particle Number/Mass Concentration

75% mass of 0.3 μm SiO2 particles 25% mass of 1 μm SiO2 particles Flow 12.5 kg/h

Particle Number Concentration Particle Mass Concentration

F1 F1´ F2 F2’ F1 F1´ F2’ F2

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METHODOLOGY DEVELOPED FOR THE EVALUATION OF THE AAA TESTS

Mass/Number Reduction Coefficient (RCM /RCNp)

𝑂𝑞𝑐 = 𝑂𝑞𝐵𝑄𝑇 𝑂𝑞𝐹𝑀𝑄𝐽 𝑆𝐷𝑂𝑞 = 1 − 𝑛𝑓𝑏𝑜 (𝑂𝑞𝑐 𝑥𝑗𝑢ℎ 𝑉𝑇) 𝑛𝑓𝑏𝑜 (𝑂𝑞𝑐 𝑥𝑗𝑢ℎ𝑝𝑣𝑢 𝑉𝑇) ∙ 100% 𝑁𝑐 = 𝑁

𝐵𝑄𝑇

𝑁𝐹𝑀𝑄𝐽 𝑆𝐷𝑛 = 1 − 𝑛𝑓𝑏𝑜 (𝑁𝑐 𝑥𝑗𝑢ℎ 𝑉𝑇) 𝑛𝑓𝑏𝑜 (𝑁𝑐 𝑥𝑗𝑢ℎ𝑝𝑣𝑢 𝑉𝑇) ∙ 100%

𝐵𝐻𝐺 =

𝑛𝐵𝑄 (𝑛𝐵𝑄+𝑛𝐺𝑄)𝐵𝑁𝑁𝐸𝐵𝑄+ 𝑛𝐺𝑄 (𝑛𝐵𝑄+𝑛𝐺𝑄)𝐵𝑁𝑁𝐸𝐺𝑄

𝐵𝑁𝑁𝐸𝑆𝑄

AMMD = Aerodynamic Median Mass Dimeter m is the mass in the phase AP (Acoustic Phase), FP (Flush Phase), RP (Reference Phase) Agglomeration Growth Factor (AGF)

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PARTICLE SIZE DISTRIBUTION STUDY

To study the ultrasonic effects on the different particles sizes sums of lognormal distributions were adjusted by least squares to the measured distributions

Fitted distributions for the AAA4 tests

F1 F2 F1´ F2´ Extracted parameters: AMMD (Aerodynamic Median Mass Diameter) and GSD (Geometric Standard Deviation) of the adjusted distributions. Increases of about 37% and 17% were

• btained respectively

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NUMBER REDUCTION COEFFICIENT (RC) AGGLOMERATION GROWTH FACTOR (AGF)

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DEVELOPMENT OF AAA MODEL

Assumptions and Basic Equation

a) Orthokinetic b) Orthokinetic with Scattering c) Mutual Radiation Pressure d) All kernels added

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DEVELOPMENT OF AAA MODEL

Comparison Model and Experimental Results Particle Number Concentration

AAA8 Comparison (Example) Measured with APS Experimental Results Simulated with Model

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DEVELOPMENT OF AAA MODEL

Comparison Experimental and Model Results Particle Number Concentration

RC = Particle Number Reduction Coefficient

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SCALING UP BOUNDARY CONDITIONS

AMMD = Aerodynamic Median Mass Diameter

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SCALING UP - SIMULATION RESULTS Number Concentration Reduction at 90%

Model Predictions Time for RCNp = 90% versus Mass Concentration

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An experimental system was developed by CSIC and tested together with CIEMAT within the PECA vessel facility for the acoustic agglomeration at 21 kHz of SiO2 (0.3, 1, and 2.5 microns) and TiO2 particles For treatment times about 80 seconds and particle number concentrations in the range 104 – 105 cm-3 the smaller particles (0.3 microns) experiment a reduction of over 90% with an acoustic intensity of about 155 dB. Under the same conditions the increase of the particle size due to ultrasound was mainly

• bserved for 1 µm particles in which increases of up to 37% were measured.

Experimental results confirmed that the ultrasound agglomeration effect improves with particle number concentration and size dispersion and is proportional to acoustic intensity and treatment time. A numerical model, based on the fundamental interaction effects acoustic waves–aerosol particles, was developed and experimentally validated. From the model the acoustic power required in case of a severe accident could be established

SYNTHESIS

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THANK YOU FOR YOUR ATTENTION! ANY QUESTIONS?

ACKNOWLEDGEMENTS: The authors thank the European Atomic Energy Community (Euratom) for showing a strong interest in the PASSAM Project, and for funding it in the frame

• f the 7th Framework Programme FP7/2007-2013 under grant agreement nº 323217

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